Jr. Gavaler et al., EFFECT OF OXYGEN OVER-DOPING ON T-C AND R(S) OF YBCO FILMS, IEEE transactions on applied superconductivity, 5(2), 1995, pp. 1173-1176
Data on bulk YBa2Cu3O7-x (YBCO) have shown that optimum critical tempe
ratures are obtained in material that has less than the maximum (stoic
hiometric) oxygen content, x=0, We have prepared films of YBCO that we
re over-doped with oxygen and have measured their properties, In some
of these films, T-c's were degraded to as low as 85K and R(s)'s to >10
m Omega (at 77K and 10 GHz). Re-annealing at 450 degrees C at experim
entally optimized oxygen pressures raised T-c's significantly in all c
ases but had only a marginal effect on R(s) values. Large improvements
in R(s) were obtained in the films which initially had very high surf
ace resistances only by annealing them at higher temperatures, Growth
and annealing conditions are described by which YBCO films with T-c's
of >90K and R(s)'s of less than or equal to 0.5 m Omega (at 77K and 10
GHz) were prepared.